Film dryer



R. B. BARNES Jan. 23, 1968 FILM DRYER Filed July 5, 1966 INVENTOR.

ROBERT BOWLING BARNES United States Patent Ofifice 3,364,593 Patented Jan. 23, 1968 3,364,593 FILM DRYER Robert Bowling Barnes, Westover Road, Stamford, Conn. 06%2 Filed July 5, 1966, Ser. No. 562,595 6 Claims. (Cl. 34150) ABSTRACT OF THE DISCLGSURE A dryer for photographic prints and negatives is described in the form of a box with slots in the top at the sides under which there are frames for holding a print or negative, the frame being formed of projecting strips, preferably a narrow one next to the box and a wider one beyond it so that a negative or print cannot fall out. The dryer has an opening in the bottom, and a lamp which does not emit actinic light. Drying is both by radiant heat and by a gentle current of warmed air flowing up over the prints and out the slots at the top.

Background of the invention Various forms of dryers for photographic prints have been designed, but they are in general not suitable or not convenient for the drying of prints and negatives which are developed within the camera back. This type of photographic equipment is being increasingly used, particularly in the cameras marketed by the Polaroid Corporation under their registered trademark Polaroid. In such cameras, after the exposure has been made, a tab is pulled out which ruptures small seed pods or capsules, setting free suitable quick developing and fixing composition. After a short period, which may range from a few seconds to a minute, it is possible to pull out the finished print and/or the negative. The print can be examined immediately, but it is not light fast, and so tends to fade under exposure to actinic light. In order to prevent this, an additional fixative composition is painted or swabbed over the print, and after drying the print then has adequate light fastness comparable to ordinary photographic prints made by older processes in which a negative is developed and prints made from it. It is important in many cases to dry the prints, particularly if they have been coated with the additional fixative, rapidly, as the wet and somewhat sticky surface can be easily damaged until it has fully dried.

Summary of the invention In the present invention prints are rapidly dried with complete safety in a box provided with slots in its top and frames for holding prints underneath each slot. There is an opening in the bottom of the box and a lamp which does not emit actinic light. The present invention thus provides for a rapid and continuous flow of warm air as well as radiation heating by non-actinic light so that as the prints dry volatile constituents are rapidly removed.

Brief description the drawing The drawing is a diagrammatic isometric view of a dryer with a portion of the lid broken away.

Description 07 the preferred embodiments The dryer is in the form of a box, of metal if desired, the side shown at I, and the top at 2. The bottom of the box 12 is provided with a central opening 9, the purpose of which will be described below. The top is cut out so as to form four slots, one along part of each of the sides. As one of the sides is broken away, and part of another side and the top also broken away, only three slots 3, 4 and appear on the drawing. Each slot leads into a rectangular frame of suitable size for the prints or films to be dried, which is formed of narrow metal side strips 6 on top of which are mounted somewhat wider strips 7, both being bolted onto the box by means of the bolts or screws 8, or otherwise fastened. A print is shown at 18 in the frame below the slot 5. Of course in operation prints may be inserted in the other frames, but they are not shown in order to avoid confusing the drawing. The frames may be of the same size or of different sizes to accommodate different prints, and when removable the same dryer can be used with different sized frames at different times, as the need arises. At the bottom of the frame there is a similar bottom piece, only the wider portion 11 showing in the drawing, although at the left side, where one of the sides of the dryer is broken away, the narrower bottom strip 14 is also apparent. The wider portion 11 is provided with a lead-in tang or projection 17 which curves into the dryer so that when a film is dropped into a slot it cannot jump over the bottom portion 11. v

In the box there is a red lamp 10 with sufficiently dense filtering in its bulb so that essentially only long-wave red and infrared is passed, and actinic rays are absorbed. This lamp screws into a socket 15 supported by bracket 13 from the bottom 12 of the box. This bottom is raised from any surface on which the box is placed by the feet 16. The lamp is connected to a suitable source of power by ordinary wires (not shown).

In operation, when from 1 to 4 prints have been exposed, developed, painted or swabbed with additional fixer, each is inserted through the slots into the frames on the sides of the dryer. The heat lamp 10 furnishes moderately intense radiant heat of non-actinic wavelengths, and a current of air enters through the bottom opening 9 and passes out through the slots at the top. Rapid drying is effected with complete safety as actinic light is kept from the drying print or film until the additional fixer has reacted and dried and the film or print is then in condition for ordinary exposure to actinic light.

While an attempt is made to swab the additional fixative only over the portion of the print or film on which the picture has actually been developed or printed, when a number of films or prints are so treated, it is almost impossible to avoid getting some of the sticky additional fixative on the edges of the print, which would touch the wider strips 7 and 11. Accordingly, it is preferred to make these strips of a material to which the additional fixative or the wet gelatine of the print itself does not readily adhere. Such a material is polytetrafiuoroethylene. This material is therefore preferred for the wider strips. Even with the material to which there' is little or no adherence of the additional fixative, after drying a large number of prints, certain material may accumulate on the strips, and so they are shown as removable with the screws 8, which permits removing them from cleaning, or to change frame sizes to fit different prints. It is much easier, of course, to clean the strips after they have been removed from the box than when they are in place, although the latter is feasible and can be performed where desirable.

As illustrated in the drawings, the dryer is shown for prints or negatives which have already been treated with additional fixative or which are merely wet negatives or prints. This is a preferred form, as the box is very cheap and rugged because of its unitary construction.

The dryer illustrated in the drawings is provided with four slots. The invention is not limited to the number of slots, and dryers with five, six, or more slots can be made where a larger number of prints are to be dried simultaneously.

The increased rapidity of drying which is possible with the present invention is illustrated by a comparative test with prints dried in the dryer of the present invention and prints dried horizontally. The test was made on a relatively humid day. Drying of prints in the normal way required 5 to 7 minutes, Whereas in the dryer of the presentinvention drying times of from 30 seconds to 1 minute produced fully and uniformly dried prints.

It is desirable to use the dryer after it has warmed up, for maximum uniformity and speed of drying. Therefore, usually the lamp in the dryer will be kept lighted all day.

Because the radiant heat from the lamp is not intense, and there is a steady flow of warm air over the surface of the drying print or negative, damage by excessive heating is minimized, and in practical operation does not present a problem with reasonable drying times which, however, are quite short. If the dryer is provided with a removable or hinged top, care should be taken that the heat lamp use-d is not of such high Wattage as to cause a surface temperature of the dryer sufficiently high to make a possible painful burn if the top of the dryer is removed or lifted and the operators hand inadvertently touches the lamp. If desired, a heat shield can be attached to the top of the dryer spaced somewhat from it to prevent excessive temperatures. However, effectiveness of the apparatus is so high that with reasonable drying times this does not present a serious problem.

The bottom of the dryer can be made detachable to facilitate replacement of the lamp and also, if desired, the top may be hinged. The dnyer operates in all cases as a chimney providing a rapid vertical movement of air over the surface of the prints being dried, and this vertical flow of air is an important feature of the invention and one of the reasons why more rapid uniform drying can be obtained than when the prints are dried horizontally.

As the fixative which is swabbed or coated onto the prints is quite sticky, it is sometimes desirable to have an inclined shelf attached to one of the dryer sides so that this operation can be effected without coming in contact with desks, tables, or other objects on which sticky fixative is to be avoided. Such a shelf may also be provided with a suitable groove or retaining flange to hold fixative swabs.

The dryer of the present invention has been described in connection with the drying of Polaroid prints, which is its most important single field. The invention is, of course, not limited to such prints or negatives, and may be used wherever rapid and uniform drying of any kind of print or negative is needed.

I claim:

1. A dryer for wet photographic material comprising in combination (a) a dryer box provided with slots along the sides in the top thereof,

(b) framing strips cooperating with said slots to form frames of photographic material size into which the material can be inserted through the slots, the framing strips being double with relatively narrow strips in contact with the dryer box sides and somewhat wider strips thereover, producing shoulders around three sides of each frame holding the photographic material when inserted,

(c) a radiant heating source which radiates only in the non-actinic range, centrally located in the dryer so that its radiant heat contacts photographic material in the various frameworks, and

(d) means for permitting air to enter the bottom of the box and to escape through the slots at the top, permitting a current of moving air over the surface of the drying photographic material.

2. A dryer according to claim 1 in which the wider strips are of polytetrafluoroethylene.

3. A dryer according to claim 2 in which the strips are removably mounted on the sides of the'dryer.

4. A dryer according to claim 1 in which the strips are removably mounted on the sides of the dryer.

5. A dryer according to claim 1 in which the dryer has a solid top except for the cut-out portions over each of the slots.

6. A dryer according to claim 2 in which the dryer has a solid top except for the cut-out portions over each of the slots.

References Cited UNITED STATES PATENTS 44,678 10/1864 Thompson 34-239 179,289 6/1876 Field 34l5l X 1,051,640 '1/1913 Sargent 34-150 2,282,070 5/1942 Mahannah 34-163 2,748,495 6/ 1956 Murray 34234 X JAMES W. WESTHAVER, Primary Examiner,

FREDERICK L. MATTESON, JR., Examiner,

A. D. HERRMANN, Assistant Examiner, 

